Controlled release urea-formaldehyde liquid fertilizer resins with high nitrogen levels

A method of producing a urea-formaldehyde resin comprising:

• 1) combining formaldehyde, urea, and ammonia in a basic solution at a formaldehyde/urea/ammonia ratio of about 5.4-3.6/1/0.45-0.65;
• 2) heating the solution to about 85 to about 95° C., and holding to ensure triazone formation;
• 3) cooling the solution to less than about 50° C., and adjusting the pH to about 9.5 to about 10.5;
• 4) adding sufficient urea and ammonia to the solution to change the ratios to about 1.1-0.6/1/0.11-0.08;
• 5) reheating the solution to about 80° C. to about reflux, at a pH of between about 9 and about 11, for about 1 to about 2.5 hours;
• and
• 6) post charging urea to bring the mole ratio to about 0.9-0.6/1/0.1-0.08;
• wherein the nitrogen content of the resin is at least about 31% based on 100% resin solids.